Deposition methods for the formation of III/V semiconductor materials, and related structures

ABSTRACT

Methods of forming ternary III-nitride materials include epitaxially growing ternary III-nitride material on a substrate in a chamber. The epitaxial growth includes providing a precursor gas mixture within the chamber that includes a relatively high ratio of a partial pressure of a nitrogen precursor to a partial pressure of one or more Group III precursors in the chamber. Due at least in part to the relatively high ratio, a layer of ternary III-nitride material may be grown to a high final thickness with small V-pit defects therein. Semiconductor structures including such ternary III-nitride material layers are fabricated using such methods.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/371,710, filed Feb. 13, 2012, now U.S. Pat. No. 8,329,571, issuedDec. 11, 2012, which is a continuation of U.S. patent application Ser.No. 13/038,920, filed Mar. 2, 2011, now U.S. Pat. No. 8,148,252, issuedApr. 3, 2012, the disclosure of each of which is hereby incorporatedherein by this reference in its entirety.

FIELD

Embodiments of the present disclosure generally relate to methods offorming III/V semiconductor materials, and to semiconductor structuresfabricated using such methods.

BACKGROUND

III/V semiconductor materials, such as, for example, III-nitrides (e.g.,indium gallium nitride (InGaN)), III-arsenides (e.g., indium galliumarsenide (InGaAs)), and III-phosphides (e.g., indium gallium phosphide(InGaP)), may be employed in various electronic, optical, andoptoelectronic devices. Examples of such devices include switchingstructures (e.g., transistors, etc.), light-emitting structures (e.g.,light-emitting diodes, laser diodes, etc.), and light-receivingstructures (e.g., waveguides, splitters, mixers, photodiodes, solarcells, solar subcells etc.). Such devices containing III/V semiconductormaterials may be used in a wide variety of applications. For example,such devices are often used to produce electromagnetic radiation (e.g.,visible light) at one or more wavelengths. The electromagnetic radiationemitted by such devices may be utilized in, for example, media storageand retrieval applications, communications applications, printingapplications, spectroscopy applications, biological agent detectionapplications, and image projection applications.

III/V semiconductor materials may be fabricated by depositing, or“growing,” a layer of III/V semiconductor material on an underlyingsubstrate. The layer of III/V semiconductor material, which iscrystalline, may be substantially comprised of a single crystal of theIII/V semiconductor material. The substrate is selected to have acrystal structure like that of the III/V semiconductor material to begrown thereon. The substrate may have a known, selected crystallographicorientation, such that the growth surface of the substrate on which theIII/V semiconductor material is to be grown comprises a knowncrystallographic plane in the crystal structure of the substratematerial. The crystalline III/V semiconductor material having a crystalstructure like that of the substrate material then may be grownepitaxially on the underlying substrate. In other words, the crystalstructure of the III/V semiconductor material may be aligned andoriented with the similar crystal structure of the underlying substrate.Although the crystal structure of the III/V semiconductor material maybe similar to that of the underlying substrate, the spacing between theatoms in a given crystallographic plane within the crystal structure ofthe III/V semiconductor material may differ (in the relaxed, equilibriumstate) from the spacing between the atoms in the correspondingcrystallographic plane within the crystal structure of the underlyingsubstrate. In other words, the relaxed lattice parameter of the III/Vsemiconductor material may differ from the relaxed lattice parameter ofthe underlying substrate material.

In greater detail, the III/V semiconductor material layer may initiallygrow “pseudomorphically” on the underlying substrate, such that theactual lattice parameter of the III/V semiconductor material is forced(e.g., by atomic forces) to substantially match the actual latticeparameter of the underlying substrate upon which it is grown. Thelattice mismatch between the III/V semiconductor material and theunderlying substrate may induce strain in the crystal lattice of theIII/V semiconductor material, and the strain results in correspondingstress within the III/V semiconductor material. The stress energy storedwithin the III/V semiconductor material may increase as the thickness ofthe layer of the III/V semiconductor material grown over the substrateincreases. If the layer of III/V semiconductor material is grown to atotal thickness equivalent to, or beyond, a thickness commonly referredto as the “critical thickness,” the III/V semiconductor material mayundergo strain relaxation. Strain relaxation in the III/V semiconductormaterial may deteriorate the crystalline quality of the III/Vsemiconductor material. For example, defects such as dislocations mayfoam in the crystal structure of the III/V semiconductor material, theexposed major surface of the layer of III/V semiconductor material maybe roughened, and/or phases may segregate within the otherwisehomogenous material, such that regions of inhomogeneity are observedwithin the layer of III/V semiconductor material.

In some cases, these defects in the III/V semiconductor material mayrender the III/V semiconductor material unsuitable for use in theultimate operational device to be formed using the III/V semiconductormaterial. For example, such defects may result in electrical shortingacross a P-N junction formed in such a III/V semiconductor material aspart of a light-emitting diode (LED) or a laser diode, such that the P-Njunction and the diode do not generate the desired electromagneticradiation.

There is a need in the art for methods of forming III/V semiconductormaterials that have smaller and/or reduced numbers of defects therein,and for semiconductor structures and devices that include such III/Vsemiconductor materials having smaller and/or reduced numbers ofdefects.

BRIEF SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described in the detailed descriptionbelow of some example embodiments of the disclosure. This summary is notintended to identify key features or essential features of the claimedsubject matter, nor is it intended to be used to limit the scope of theclaimed subject matter.

In some embodiments, the present disclosure includes methods of formingindium gallium nitride (InGaN). In accordance with such methods, a layerof gallium nitride (GaN) is provided within a chamber. A layer of InGaNis epitaxially grown on a surface of the layer of GaN. Epitaxial growthof the layer of InGaN includes providing a precursor gas mixture withinthe chamber, selecting the precursor gas mixture to comprise one or moreGroup III precursors and a nitrogen precursor, and formulating theprecursor gas mixture to cause a ratio of a partial pressure of thenitrogen precursor to a partial pressure of the one or more Group IIIprecursors within the chamber to be at least about 5,600. At least aportion of the one or more Group III precursors and at least a portionof the nitrogen precursor are decomposed proximate the surface of thelayer of GaN to grow the layer of InGaN. The layer of InGaN is grown toan average final thickness greater than about one hundred nanometers(100 nm).

In additional embodiments, the present disclosure includes methods offorming a ternary III-nitride material comprising nitrogen, gallium, andat least one of indium and aluminum. In accordance with such methods, abinary III-nitride material is provided within a chamber, and a layer ofternary III-nitride material is epitaxially grown on the binaryIII-nitride material. Epitaxial growth of the ternary III-nitridematerial includes providing a precursor gas mixture within the chamberthat includes a nitrogen precursor and two or more Group III precursors,and formulating the precursor gas mixture such that a ratio of a partialpressure of the nitrogen precursor to a partial pressure of the one ormore Group III precursors within the chamber is at least about 5,600.The nitrogen precursor and the two or more Group III precursors aredecomposed in the chamber to form the layer of ternary III-nitridematerial. The layer of ternary III-nitride material is grown to anaverage final thickness greater than about one hundred nanometers (100nm). The layer of ternary III-nitride material is formulated such that arelaxed lattice parameter mismatch between the layer of ternaryIII-nitride material and the binary III-nitride material is at leastabout 0.5% of the relaxed average lattice parameter of the binaryIII-nitride material. A plurality of V-pits are formed in the layer ofternary III-nitride material, and the V-pits are formed such that theyhave an average pit width of about two hundred nanometers (200 nm) orless in the fully grown layer of ternary III-nitride material.

The present disclosure also includes methods of forming a stack oflayers of III-nitride material. In such methods, a substrate is providedwithin a chamber, and at least one layer of GaN and a plurality oflayers of InGaN are epitaxially grown over the substrate within thechamber. The stack of layers of III-nitride material is formed to have afinal average total thickness greater than about one hundred nanometers(100 nm). Additionally, epitaxial growth of at least one layer of InGaNof the plurality of layers of InGaN comprises providing a precursor gasmixture within the chamber, selecting the precursor gas mixture tocomprise one or more Group III precursors and a nitrogen precursor,formulating the precursor gas mixture to cause a ratio of a partialpressure of the nitrogen precursor to a partial pressure of the one ormore Group III precursors within the chamber to be at least about 5,600,and decomposing at least a portion of the one or more Group IIIprecursors and at least a portion of the nitrogen precursor to form theat least one layer of InGaN.

In yet further embodiments, the present disclosure includessemiconductor structures fabricated using methods as disclosed herein.For example, in some embodiments, a semiconductor structure includesInGaN. The InGaN is formed by providing a layer of GaN within a chamber,and epitaxially growing a layer of InGaN on a surface of the layer ofGaN. Epitaxial growth of the layer of InGaN includes providing aprecursor gas mixture within the chamber, selecting the precursor gasmixture to comprise one or more Group III precursors and a nitrogenprecursor, and formulating the precursor gas mixture to cause a ratio ofa partial pressure of the nitrogen precursor to a partial pressure ofthe one or more Group III precursors within the chamber to be at leastabout 5,600. At least a portion of the one or more Group III precursorsand at least a portion of the nitrogen precursor are decomposedproximate the surface of the layer of GaN to form the layer of InGaN.The fully grown layer of InGaN has an average final thickness greaterthan about one hundred nanometers (100 nm) and comprises a plurality ofV-pits therein having an average pit width of about two hundrednanometers (200 nm) or less. Further, a relaxed lattice parametermismatch between the fully grown layer of InGaN and the layer of GaN isat least about 0.5% of the relaxed average lattice parameter of thelayer of GaN.

In additional embodiments, a semiconductor structure includes a ternaryIII-nitride material comprising nitrogen, gallium, and at least one ofindium and aluminum. The ternary III-nitride material is formed byproviding a substrate comprising a binary III-nitride material within achamber, and epitaxially growing a layer of ternary III-nitride materialon the binary III-nitride material. Epitaxial growth of the layer ofternary III-nitride material includes providing a precursor gas mixturewithin the chamber, wherein the precursor gas mixture includes anitrogen precursor and two or more Group III precursors, and formulatingthe precursor gas mixture such that a ratio of a partial pressure of thenitrogen precursor to a partial pressure of the one or more Group IIIprecursors within the chamber is at least about 5,600. The nitrogenprecursor and the two or more Group III precursors are decomposed in thechamber to form the ternary III-nitride material. The fully grown layerof ternary III-nitride material has an average final thickness greaterthan about one hundred nanometers (100 nm) and comprises a plurality ofV-pits therein having an average pit width of about two hundrednanometers (200 nm) or less. Further, a relaxed lattice parametermismatch between the fully grown layer of ternary III-nitride materialand the binary III-nitride material is at least about 0.5% of therelaxed average lattice parameter of the binary III-nitride material.

Further aspects, details, and alternate combinations of the elements ofembodiments of the disclosure will be apparent from the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure may be understood more fully by referenceto the following detailed description of example embodiments, which areillustrated in the appended figures in which:

FIG. 1 is a graph that may be used to approximate the relaxed latticeparameter of InGaN as a function of indium content therein;

FIG. 2 is a simplified, schematically illustrated cross-sectional sideview of a substrate on or over which a III/V semiconductor material maybe deposited;

FIG. 3 is a simplified, schematically illustrated cross-sectional sideview of a semiconductor structure that includes a first III/Vsemiconductor material deposited on a surface of the substrate of FIG.2;

FIG. 4 is a simplified, schematically illustrated cross-sectional sideview of a semiconductor structure that includes a second III/Vsemiconductor material deposited on the first III/V semiconductormaterial of FIG. 3 on a side thereof opposite the substrate of FIG. 2;

FIG. 5 is a simplified, schematically illustrated perspective view of aportion of the semiconductor structure of FIG. 4 and illustrates a V-pitin the second III/V semiconductor material;

FIG. 6 is a graph illustrating the observed variation in average widthof V-pits formed in ternary III/V semiconductor material as a functionof variation in elastic energy within the ternary III/V semiconductormaterial for different ranges of the ratio of Group V precursors toGroup III precursors; and

FIG. 7 is a simplified, schematically illustrated cross-sectional sideview like that of FIG. 4, illustrating another embodiment of asemiconductor structure that includes a plurality of alternating layersof binary and ternary III/V semiconductor materials over a substrate,and illustrates V-pits formed within the alternating layers of binaryand ternary III/V semiconductor materials.

DETAILED DESCRIPTION

The illustrations presented herein are not meant to be actual views ofany particular material, device, or method, but are merely idealizedrepresentations, which are employed to describe embodiments of thepresent disclosure.

The following description provides specific details, such as materialtypes and processing conditions, in order to provide a thoroughdescription of embodiments of the present disclosure and implementationthereof. However, a person of ordinary skill in the art will understandthat the embodiments of the present disclosure may be practiced withoutemploying these specific details and in conjunction with conventionalfabrication techniques. In addition, the description provided hereindoes not form a complete process flow for manufacturing a semiconductorstructure or device. Only those process acts and structures necessary tounderstand the embodiments of the present disclosure are described indetail herein.

As used herein, the term “semiconductor structure” means and includesany structure that is used in the formation of a semiconductor device.Semiconductor structures include, for example, dies and wafers (e.g.,carrier substrates and device substrates), as well as assemblies orcomposite structures that include two or more dies and/or wafersthree-dimensionally integrated with one another. Semiconductorstructures also include fully fabricated semiconductor devices, as wellas intermediate structures formed during fabrication of semiconductordevices. Semiconductor structures may comprise conductive materials,semiconductive materials, non-conductive materials (e.g., electricalinsulators), and combinations thereof.

As used herein, the term “III/V semiconductor material” means andincludes any semiconductor material that is at least predominantlycomprised of one or more elements from Group IIIA of the periodic table(B, Al, Ga, In, and Ti) and one or more elements from Group VA of theperiodic table (N, P, As, Sb, and Bi). For example, III/V semiconductormaterials include, but are not limited to, GaN, GaP, GaAs, InN, InP,InAs, AlN, AlP, AlAs, InGaN, InGaP, InGaNP, etc.

As used herein, the term “III-nitride semiconductor material” means andincludes any III/V semiconductor material that is at least comprised ofone or more elements from Group IIIA of the periodic table (B, Al, Ga,In, and Tl) and nitrogen. For example, III-nitride semiconductormaterials include GaN, InN, AlN, InGaN, GaAlN, InAlN, etc.

As used herein, the terms “indium gallium nitride” and “InGaN” meanalloys of indium nitride (InN) and gallium nitride (GaN) having acomposition of In_(x)Ga_(1-x)N, where 0<x<1.

As used herein, the teen “critical thickness” means the average totalthickness of a layer of semiconductor material at which, and beyondwhich, pseudomorphic growth discontinues and the layer undergoes strainrelaxation.

As used herein, the term “growth surface” means any surface of asemiconductor substrate or layer at which additional growth of thesemiconductor substrate or layer can be carried out.

As used herein, the terms “chemical vapor deposition” and “CVD” aresynonymous and mean and include any process used to deposit solidmaterial(s) on a substrate in a reaction chamber in which the substrateis exposed to one or more reagent gasses, which react, decompose, orboth react and decompose in a manner that results in the deposition ofthe solid material(s) on a surface of the substrate.

As used herein, the terms “vapor phase epitaxy” and “VPE” are synonymousand mean and include any CVD process in which the substrate is exposedto one or more reagent vapors, which react, decompose, or both react anddecompose in a manner that results in the epitaxial deposition of thesolid material(s) on a surface of the substrate.

As used herein, the terms “halide vapor phase epitaxy” and “HYPE” aresynonymous and mean and include any VPE process in which at least onereagent vapor used in the VPE process comprises a halide vapor.

As used herein, the term “substantially” refers to a result that iscomplete except for any deficiencies normally expected in the art.

Embodiments of the disclosure may have applications to a wide range ofIII/V semiconductor materials. For example, the methods and structuresof the embodiments of the disclosure may be applied to III-nitrides,III-arsenides, III-phosphides and III-antimonides. Particularapplications pertain to growing ternary Group III-nitride semiconductormaterials containing indium, such as indium gallium nitride (InGaN).Accordingly, the following description and figures focus particularly onInGaN, although InGaN is a non-limiting example embodiment, andadditional embodiments may include the formation of other ternary III/Vsemiconductor materials.

A ternary III-nitride layer grown heteroepitaxially to a thickness abovea critical thickness may undergo strain relaxation to relieve strain inthe crystal lattice resulting from lattice mismatch. Upon the onset ofstrain relaxation in the ternary III-nitride material, an increasedamount of a Group III element, such as indium or aluminum, may beincorporated into the layer of ternary III-nitride material duringgrowth, which may result in a non-uniform concentration profile of theGroup III element across a thickness of the layer of ternary III-nitridematerial. For example, an InGaN layer may include an increased indiumpercentage proximate to a growth surface of the layer relative toproximate an underlying substrate or other material. Such a non-uniformindium composition in the InGaN layer may be undesirable for at leastsome applications.

Additionally, the strain relaxation of the ternary III-nitride layer mayalso result in roughening of the growth surface of the ternaryIII-nitride layer. Such surface roughening may be detrimental to theproduction of semiconductor devices using the ternary III-nitride layer.Further, strain relaxation in a ternary III-nitride layer may result inan increased density of defects in the crystalline structure of theternary III-nitride material. Such defects may include, for example,dislocations and regions of inhomogeneous composition (i.e.,phase-separated regions).

As a non-limiting example, for the case of InGaN (a III-nitridematerial), InGaN layers may be deposited heteroepitaxially on anunderlying substrate, which may have a crystal lattice that does notmatch that of the overlying InGaN layer. For example, InGaN layers maybe deposited on a semiconductor substrate comprising gallium nitride(GaN). The GaN may have a relaxed (i.e., substantially strain free)in-plane lattice parameter of approximately 3.189 Å, and the InGaNlayers may have a relaxed in-plane lattice parameter, depending on thecorresponding percentage of indium content, of approximately 3.21 Å (for7% indium, i.e., In_(0.07)Ga_(0.93)N), approximately 3.24 Å (for 15%indium, i.e., In_(0.15)Ga_(0.85)N), and approximately 3.26 Å (for 25%indium, i.e., In_(0.25)Ga_(0.75)N). FIG. 1 is a graph illustrating thesedata points, and shows a line fitted to these data points. The equationof the line is given by y=0.0027x+3.1936, and this linear equation maybe used to approximate the lattice parameter of InGaN as a function ofindium content over the range extending from about 5% to about 25%,wherein x is the percentage of indium in the InGaN and y is the relaxedin-plane lattice parameter of the InGaN.

FIGS. 2 through 4 are used to illustrate the fabrication of a layer ofternary III/V semiconductor material in accordance with embodiments ofthe disclosure, and, in particular, a layer of InGaN 20, which is shownin FIG. 4. Referring to FIG. 2, a substrate 10 may be provided. Thesubstrate 10 may be at least substantially comprised of a ceramic suchas an oxide (e.g., silicon dioxide (SiO₂) or aluminum oxide (Al₂O₃)(e.g., sapphire, which is α-Al₂O₃)) or a nitride (e.g., silicon nitride(Si₃N₄) or boron nitride (BN)). As additional examples, the substrate 10may be at least substantially comprised of a semiconductor material suchas silicon (Si), germanium (Ge), a III/V semiconductor material, etc.The substrate 10 may have a crystalline structure, and the crystalstructure of the substrate 10 may have a known, selected orientation,such that an exposed major surface 12 of the substrate 10 over which thelayer of InGaN 20 (FIG. 4) is to be grown comprises a known, selectedcrystallographic plane of the crystal structure of the substrate 10. Forexample, the substrate 10 may comprise sapphire with a (0001)crystallographic orientation, which is often referred to as “c-planesapphire.”

Referring to FIG. 3, optionally, a layer of a binary III/V semiconductormaterial, such as a layer of GaN 16 may be formed on the major surface12 of the substrate 10. The layer of GaN 16 may comprise what arereferred to in the art as “buffer” layers or “transition” layers. TheGaN 16 may be substantially crystalline, and may be at leastsubstantially comprised by a single crystal of GaN. The layer of GaN 16may have an average total thickness in a range extending from about twonanometers (2 nm) to about one hundred microns (100 μm). The figuresherein are not drawn to scale, and, in actuality, the layer of GaN 16may be relatively thin compared to the substrate 10.

Optionally, one or more intermediate layers of material (not shown),such as another layer of semiconductor material, may be disposed betweenthe layer of GaN 16 and the substrate 10. Such intermediate layers ofmaterial may be used, for example, as a seed layer for forming the layerof GaN 16 thereon, or as a bonding layer for bonding the layer of GaN 16to the substrate 10. Such bonding processes may be used when it isdifficult or impossible to form the layer of GaN 16 directly on thesubstrate 10. In addition, bonding of the layer of GaN 16 to thesubstrate 10 may be desired if the layer of GaN 16 has a polar crystalorientation. In such embodiments, the bonding process may be utilized toalter the polarity of the polar GaN, or to provide the growth surface ofthe GaN with a desirable polarity.

The layer of GaN 16 may be formed on the major surface 12 of thesubstrate 10 using a chemical vapor deposition (CVD) process, such as ametalorganic chemical vapor deposition (MOCVD) process, a molecular beamepitaxy (MBE) process, or a metal halide vapor phase epitaxy (HVPE)process. HVPE systems and processes that may be employed to form thelayer of GaN 16 are disclosed, for example, in U.S. Patent ApplicationPublication No. 2009/0223442 A1, which published Sep. 10, 2009 in thename of Arena et al., provisional U.S. Patent Application Ser. No.61/157,112, which was filed Mar. 3, 2009 in the name of Arena et al.,U.S. patent application Ser. No. 12/894,724, which was filed Sep. 30,2010 in the name of Bertram, and provisional U.S. Patent ApplicationSer. No. 61/416,525, which was filed Nov. 23, 2010 in the name of Arenaet al., the disclosure of each of which is incorporated herein in itsentirety by this reference. Briefly, in such HVPE processes, epitaxialgrowth of the layer of GaN 16 on the surface 12 of the substrate 10 mayresult from a vapor phase reaction between gallium mono-chloride (GaCl)and ammonia (NH₃) that is carried out within a reaction chamber atelevated temperatures between about 500° C. and about 1,000° C. The NH₃may be supplied from a standard source of NH₃ gas. In some methods, theGaCl vapor is provided by passing hydrogen chloride (HCl) gas (which maybe supplied from a standard source of HCl gas) over heated liquidgallium (Ga) to form GaCl in situ within the reaction chamber. Theliquid gallium may be heated to a temperature of between about 750° C.and about 850° C. The GaCl and the NH₃ may be directed to (e.g., over)the major surface 12 of the substrate 10, which may be heated.

The layer of GaN 16 may have a crystal structure like that of thesubstrate 10, and may be grown epitaxially on the substrate 10. In otherwords, the crystal structure of the layer of GaN 16 may be aligned andoriented with a similar crystal structure of the underlying substrate10. Although the crystal structure of the layer of GaN 16 may be similarto that of the underlying substrate 10, the relaxed lattice parameter ofthe layer of GaN 16 may differ from the relaxed lattice parameter of thesubstrate 10. As a result, certain imperfections or defects may beformed within the crystal structure of the layer of GaN 16. For example,dislocations 18 (e.g., edge dislocations and/or screw dislocations) maybe present in the crystal structure of the layer of GaN 16, as shown inFIG. 3. At least some such dislocations 18 may originate at theinterface between the layer of GaN 16 and the major surface 12 of thesubstrate 10. While only two dislocations 18 are shown in the simplifiedillustration of FIG. 3, in reality, the density of such dislocations 18in the layer of GaN 16 may be as high as one hundred thousand per squarecentimeter (10⁵/cm²), or even as high as one million per squarecentimeter (10⁶/cm²) or more. Any of various methods known in the artmay be used to reduce the density of dislocations 18 in the layer of GaN16, as the layer of GaN 16 is formed. Such methods include, for example,epitaxial lateral overgrowth (ELO), pendeo-epitaxy, in-situ maskingtechniques, etc.

Referring to FIG. 4, a layer of ternary III/V semiconductor material,such as a layer of InGaN 20, may be epitaxially grown or otherwiseformed on a major surface 17 (FIG. 3) of the layer of GaN 16. The layerof InGaN 20 may be substantially crystalline, and may be at leastsubstantially comprised by a single crystal of InGaN. The layer of InGaN20 may have an average final total thickness T greater than about onehundred nanometers (100 nm). In some embodiments, the average finaltotal thickness T may be greater than about one hundred and fiftynanometers (150 nm), or even greater than about two hundred nanometers(200 nm), and may be less than a critical thickness of the layer ofInGaN 20.

The layer of InGaN 20 may be deposited on the major surface 17 of thelayer of GaN 16 using a chemical vapor deposition (CVD) process, such asa metalorganic chemical vapor deposition (MOCVD) process, a molecularbeam epitaxy (MBE) process, or a metal halide vapor phase epitaxy (HVPE)process. HVPE systems and processes that may be employed to form thelayer of InGaN 20 are disclosed, for example, in the aforementioned U.S.Patent Application Publication No. US 2009/0223442 A1, which publishedSep. 10, 2009 in the name of Arena et al., provisional U.S. PatentApplication Ser. No. 61/157,112, which was filed Mar. 3, 2009 in thename of Arena et al., U.S. patent application Ser. No. 12/894,724, whichwas filed Sep. 30, 2010 in the name of Bertram, and provisional U.S.Patent Application Ser. No. 61/416,525, which was filed Nov. 23, 2010 inthe name of Arena et al. The layer of InGaN 20 may be formulated to havea composition of In_(x)Ga_((1-x))N, wherein x is at least about 0.05. Insome embodiments, x may be between about 0.05 and about 0.10. In otherwords, the indium content in the layer of InGaN 20 may be between aboutfive atomic percent (5 at %) and about ten atomic percent (10 at %).

The layer of GaN 16 may have a relaxed (i.e., substantially strainfree), in-plane (i.e., in the plane parallel to the growth surface)lattice parameter of approximately 3.189 Å, and the layer of InGaN 20may have a relaxed in-plane lattice parameter, depending on thecorresponding percentage of indium content. As previously mentioned, thelayer of InGaN 20 may have a relaxed in-plane lattice parameter ofapproximately 3.21 Å for 7 at % indium (i.e., In_(0.07)Ga_(0.93)N).Additionally, using the equation of the line as given byy=0.0027x+3.1936 as shown in the graph of FIG. 1 to estimate the relaxedin-plane lattice parameter, the layer of InGaN 20 may have a relaxedin-plane lattice parameter of approximately 3.207 Å for 5 at % indium(i.e., In_(0.05)G_(0.95)N), and a relaxed in-plane lattice parameter ofapproximately 3.220 Å for 10 at % indium (i.e., In_(0.10)Ga_(0.90)N).

In some embodiments, a relaxed lattice parameter mismatch between thelayer of InGaN 20 and the layer of GaN 16 may be between about 0.5% andabout 1.0% of the relaxed average lattice parameter of the layer of GaN16. The relaxed lattice parameter mismatch may be determined using theequation M=100((a₂−a₁)/a₁), wherein M is the relaxed lattice parametermismatch, a₁ is the relaxed average lattice parameter of the layer ofGaN 16, and a₂ is the relaxed average lattice parameter of the layer ofInGaN 20. For example, when the layer of InGaN 20 includes 5 at % indiumand has a relaxed in-plane lattice parameter of approximately 3.207 Å, arelaxed lattice parameter mismatch between the layer of InGaN 20 and thelayer of GaN 16 may be about 0.56% (i.e., 0.56=100((3.207-3.189)/3.189))of the relaxed average lattice parameter of the layer of GaN 16. Whenthe layer of InGaN 20 includes 10 at % indium and has a relaxed in-planelattice parameter of approximately 3.220 Å, a relaxed lattice parametermismatch between the layer of InGaN 20 and the layer of GaN 16 may beabout 0.97% of the relaxed average lattice parameter of the layer of GaN16.

As a result of the mismatch between the relaxed lattice parameters ofthe layer of GaN 16 and the layer of InGaN 20, the layer of InGaN 20will grow lattice mismatched on the layer of GaN 16. Generally, thelattice mismatched growth (i.e., mismatch between the layer of InGaN 20and the layer of GaN 16) is accompanied with strain relaxation when thestrain energy stored in the layer of InGaN 20 is greater than the strainenergy that will result in nucleation of additional dislocations 18′within the layer of InGaN 20. This lattice mismatched growth occurs fora lattice arranged in cubic systems but is more complex for materialswith hexagonal lattice structure like GaN, InGaN, and AlGaN. Inhexagonal layers, there may not be an easy gliding plane fordislocations, and, therefore, much higher strain energy may be stored inthe layer of InGaN 20 prior to nucleating dislocations therein. Uponreaching plastic relaxation, relaxation may occur by modification of anexposed major surface 22 (FIG. 5) of the layer of InGaN 20, which is thegrowth surface thereof. When the growth surface comprises the (0001)plane in the hexagonal crystal structure, pit defects 30 may occur.These pit defects 30 appear as inverted pyramids with an apex at or neara dislocation 18, 18′ (e.g., a threading dislocation) and are referredto hereinafter as V-pits 30. As the layer of InGaN 20 grows, the sizesof the V-pits 30 also grow.

FIG. 5 is a simplified isometric drawing illustrating a V-pit 30 in thelayer of InGaN 20. The V-pit 30 extends into the exposed major surface22 of the layer of InGaN 20, which is the growth surface of the layer ofInGaN 20. The hexagonal shape of the opening on the growth surface 22results from the hexagonal crystal structure of the InGaN material. TheV-pit 30 is defined by sidewalls 24 (facets) of the layer of InGaN 20within the V-pit 30, which extend from an apex 26 of the V-pit 30 to theexposed major surface 22 of the layer of InGaN 20. The apex 26 is thelocation at which the V-pit 30 originated during growth of the layer ofInGaN 20.

As shown in FIG. 5, the V-pit 30 has a pit depth D, which is thedistance the V-pit 30 extends into the layer of InGaN 20 (i.e., theshortest distance from the apex 26 to the plane of the exposed majorsurface 22 of the layer of InGaN 20). Additionally, the V-pit 30 has apit width W, which is the distance across the opening of the V-pit 30 inthe plane of the exposed major surface 22 of the layer of InGaN 20 fromone side thereof (as defined by the intersection between a sidewall 24with the exposed major surface 22) to an opposing side thereof (asdefined by the intersection between an opposing sidewall 24 and theexposed major surface 22). The pit widths W of V-pits 30 formed in thelayers of InGaN 20 may be measured using, for example, Atomic ForceMicroscopy (AFM). V-pits 30 generally have a fixed ratio of pit width Wto pit depth D, which is due to the nature and orientation of thecrystal structure. Therefore, the pit depth D of a V-pit 30 can beestimated based on a measured pit width W of the V-pit 30. In otherwords, from crystallographic considerations (e.g., the angle between the(00010-00011) and (0001) planes), the pit depth D can be calculated fromthe measured pit width W (see, e.g., J. E. Northrup, L. T. Romano, J.Neugebauer, Appl. Phys. Lett. 74(16), 2319 (1999)).

Referring again to FIG. 4, the layer of InGaN 20 may includedislocations 18, 18′ that extend within the layer of GaN 16 and into thelayer of InGaN 20, that originate at the interface between the layer ofGaN 16 and the layer of InGaN 20 and extend into the layer of InGaN 20,and that originate and extend within the layer of InGaN 20. V-pits 30may result from any such dislocations 18, 18′. V-pits 30 having an apex26 proximate the interface between the layer of InGaN 20 and the layerof GaN 16 are relatively larger (i.e., have a wider pit width W and adeeper pit depth D) compared to V-pits 30 having an apex 26 at anintermediate location within the layer of InGaN 20.

In some applications, the layer of InGaN 20 may be separated from theunderlying layer of GaN 16 and transferred to another substrate forfurther processing and device fabrication after the layer of InGaN 20has been grown on the layer of GaN 16. Relatively large V-pits 30, suchas those that originate proximate the interface between the layer ofInGaN 20 and the layer of GaN 16, can result in holes that extend atleast substantially entirely through the layer of InGaN 20 after thelayer of InGaN 20 has been transferred in such a process. The V-pits 30may also adversely affect the processes used to separate the layer ofInGaN 20 from the layer of GaN 16 and transfer the layer of InGaN 20 toanother substrate. The presence of the V-pits 30 in the layer of InGaN20 may adversely affect light-emitting diodes (LEDs) formed from thelayer of InGaN 20. For example, if a V-pit 30 extends across the entirethickness of the layer of InGaN 20, it may short out the diode portionof an LED device including the portion of the layer of InGaN 20 in whichthe V-pit 30 is disposed, rendering the LED device inoperable.

The strain energy stored within the layer of InGaN 20 is proportional tothe average total thickness T of the layer of InGaN 20, and to theconcentration of indium in the layer of InGaN 20. Thus, the relativedifference in the strain energy stored within the layer of InGaN 20 fordifferent indium contents and average total thicknesses T for the layerof InGaN 20 may be estimated using the relationship E_(E)∝T(C_(In)),wherein E_(E) is the elastic energy within the layer of InGaN 20 (inarbitrary units), T is the average total thicknesses of the layer ofInGaN 20, and C_(In) is the concentration of indium in the layer ofInGaN 20 expressed as an atomic percentage. For example, if the layer ofInGaN 20 has an average total thickness T of one hundred and fiftynanometers (150 nm) and an indium concentration of 8.5 at %, the elasticenergy E_(E) within the layer of InGaN 20 may be about 1,275(1,275=150(8.5)). If, however, the layer of InGaN 20 has an averagetotal thickness T of two hundred nanometers (200 nm) and an indiumconcentration of 9.0 at %, the elastic energy E_(E) within the layer ofInGaN 20 may be about 1,800 (1,800=200(9.0)).

Thus, relatively thin layers of InGaN 20 will have lower elastic energytherein, and can be grown with few or no V-pits 30. However, for someapplications, a relatively thicker layer of InGaN 20 may be desirable.As a consequence, with conventional processing, V-pits 30 are present inthe relatively thicker layer of InGaN 20 and the V-pits 30 become deeperand wider with increasing thickness of the layer of InGaN 20.

Embodiments of the present disclosure may be used to reduce the size ofV-pits 30 formed when a layer of ternary III-nitride material, such as alayer of InGaN 20, is formed over a layer of binary III-nitridematerial, such as a layer of GaN 16. Thus, for a given average totalthickness of the layer of ternary III-nitride material, the V-pits 30may have a relatively smaller pit width and/or pit depth when the layerof ternary III-nitride material is formed in accordance with embodimentsof methods disclosed herein, relative to previously known methods forforming such layers of ternary III-nitride material.

As previously mentioned, the layer of InGaN 20 may be deposited on themajor surface 17 of the layer of GaN 16 using a chemical vapordeposition (CVD) process, such as a metalorganic chemical vapordeposition (MOCVD) process, a molecular beam epitaxy (MBE) process, or ametal halide vapor phase epitaxy (HVPE) process. Such processes may becarried out within an enclosed chamber (e.g., a deposition or reactionchamber). The substrate 10 and the layer of GaN 16 thereon may beprovided within the chamber. The chamber, and the substrate 10 and thelayer of GaN 16 therein, may be heated to a temperature or temperaturesbetween about 500° C. and about 1,000° C. A precursor gas mixture isintroduced or otherwise provided within the chamber. To form aIII-nitride semiconductor material, the precursor gas mixture isselected to comprise one or more Group III precursors and a nitrogenprecursor. At least a portion of the one or more Group III precursorsand at least a portion of the nitrogen precursor decompose within theheated chamber proximate the surface on which the III-nitridesemiconductor material is to be formed. Upon decomposition, theelemental species deposit and combine in an ordered manner on the growthsurface to form the III-nitride semiconductor material.

The precursor gas mixture optionally may include additional gasses orreactants, such as inert gasses (e.g., nitrogen) and/or reactant speciesused to incorporate dopants into the layer of InGaN 20. As non-limitingexamples, silane (SiH₄) may be introduced as an N-type dopant, andmagnesium may be introduced as a P-type dopant.

The nitrogen precursor may comprise, for example, ammonia (NH₃). The oneor more Group III precursors may comprise, for example, one or more oftrimethylindium (TMI), triethylindium (TEI), and triethylgallium (TEG).The nitrogen precursor and the one or more Group III precursors may bepresent within the chamber as gasses and/or vapors (the term “gas” asused herein encompassing both gasses and vapors), and the precursors maybe caused to flow through the chamber during processing. The chamber maybe under vacuum (i.e., the pressure within the chamber may be belowatmospheric pressure) during processing.

In accordance with embodiments of the disclosure, the precursor gasmixture may be formulated in such a manner as to cause a ratio of apartial pressure of the nitrogen precursor to a partial pressure of theone or more Group III precursors within the chamber to be in a rangeextending from about 5,600 to about 6,600. It has been discovered thatsuch a high ratio of the nitrogen precursor to a partial pressure of theone or more Group III precursors may result in V-pits 30 formed in thelayer of InGaN 20 to be relatively smaller when compared to layers ofInGaN 20 formed with relatively lower partial pressure ratios. Forexample, referring again to FIG. 5, in accordance with some embodiments,the average pit width W of the V-pits 30 in a layer of InGaN 20 formedas described herein may be about two hundred nanometers (200 nm) orless, or even about one hundred and fifty nanometers (150 nm) or less.Further, in such embodiments, the layer of InGaN 20 may have an averagetotal thickness T (FIG. 4) of greater than about one hundred nanometers(100 nm), greater than about one hundred and fifty nanometers (150 nm),or even greater than about two hundred nanometers (200 nm).

As known in the art, the partial pressures of the precursors within thechamber are related to the flow rates of the precursors through thechamber. Thus, the partial pressures of the precursors within thechamber may be selectively controlled and tailored by selectivelycontrolling and tailoring the flow rates of the precursors through thechamber.

FIG. 6 is a graph illustrating the observed variation in average pitwidth W of V-pits 30 formed in a layer of InGaN 20 as a function ofvariation in elastic energy within the layers of InGaN 20 for differentranges of the ratio of a partial pressure of the nitrogen precursor to apartial pressure of the one or more Group III precursors within thechamber during the respective depositions of the layers of InGaN 20. Aspreviously mentioned, the relative difference in the strain energystored within layers of InGaN 20 for different indium contents andaverage total thicknesses T for the layer of InGaN 20 may be estimatedusing the relationship E_(E)∝T(C_(In)), wherein E_(E) is the elasticenergy within the layer of InGaN 20 (in arbitrary units), T is theaverage total thicknesses of the layer of InGaN 20, and C_(h), is theconcentration of indium in the layer of InGaN 20 expressed as an atomicpercentage. The elastic energies in FIG. 6 were determined bymultiplying the average total thicknesses T of the layers of InGaN 20 innanometers by the respective indium concentrations in the layers ofInGaN 20.

The circles in the chart of FIG. 6 correspond to the layers of InGaN 20fabricated using processes in which the ratio of the partial pressure ofthe nitrogen precursor to the partial pressure of the one or more GroupIII precursors within the chamber during deposition was within the rangeextending from about 3,071 to about 5,461. In contrast, the triangles inthe chart of FIG. 6 correspond to the layers of InGaN 20 fabricatedusing processes according to embodiments of methods as disclosed herein,in which the ratio of the partial pressure of the nitrogen precursor tothe partial pressure of the one or more Group III precursors within thechamber during deposition was within the range extending from about5,600 to about 6,600. The trend line 50 in FIG. 6 approximates therelationship between the elastic energy within the layers of InGaN 20and the measured pit widths W of the V-pits 30 formed therein for thesamples fabricated using processes in which the partial pressure ratiowas within the range extending from about 3,071 to about 5,461, asmentioned above. Similarly, the trend line 52 in FIG. 6 approximates therelationship between the elastic energy within the layers of InGaN 20and the measured pit widths W of the V-pits 30 faulted therein for thesamples fabricated using processes in which the partial pressure ratiowas within the range extending from about 5,600 to about 6,600, asdescribed above. As can be seen by comparing the trend line 50 with thetrend line 52 in the chart of FIG. 6, for any given elastic energywithin the layers of InGaN 20, the measured pit widths W of the V-pits30 are relatively smaller in the samples fabricated using processes inwhich the partial pressure ratio was within the range extending fromabout 5,600 to about 6,600, relative to the measured pit widths W of theV-pits 30 in the samples fabricated using processes in which the partialpressure ratio was within the range extending from about 3,071 to about5,461.

As an example, the vertical line 54 in FIG. 6 is located at an elasticenergy of 1,800, and may correspond to layers of InGaN 20 having anaverage total thickness T of about two hundred nanometers (200 nm) andan indium content of nine atomic percent (9 at %) (i.e., 1,800=200(9)).As shown in the chart of FIG. 6, such a layer of InGaN 20 fabricatedusing processes in which the partial pressure ratio was within the rangeextending from about 5,600 to about 6,600 as described herein may beexpected to include V-pits 30 having pit widths W of about one hundredand sixty nanometers (160 nm). In contrast, such a layer of InGaN 20fabricated using processes in which the partial pressure ratio waswithin the range extending from about 3,071 to about 5,461 may beexpected to include V-pits 30 having larger pit widths W of about twohundred and sixty nanometers (260 nm). As another example, the verticalline 56 in FIG. 6 is located at an elastic energy of 1,275, and maycorrespond to layers of InGaN 20 having an average total thickness T ofabout one hundred and fifty nanometers (150 nm) and an indium content ofeight and one-half atomic percent (8.5 at %) (i.e., 1,275=150(8.5)). Asshown in the chart of FIG. 6, such a layer of InGaN 20 fabricated usingprocesses in which the partial pressure ratio was within the rangeextending from about 5,600 to about 6,600 as described herein may beexpected to include V-pits 30 having pit widths W of less than onehundred nanometers (100 nm). In contrast, such a layer of InGaN 20fabricated using processes in which the partial pressure ratio waswithin the range extending from about 3,071 to about 5,461 may beexpected to include V-pits 30 having larger pit widths W of about onehundred and seventy nanometers (170 nm).

Without being bound to any theory, it is currently believed that byemploying relatively high precursor gas ratios during growth of thelayer of InGaN 20, as described herein, the rate at which additionalInGaN material is grown on the sidewalls 24 within the V-pits 30 may beincreased relative to the rate at which additional InGaN material isgrown on the exposed major surface 22 (the growth surface) to result inV-pits 30 of relatively smaller size.

Thus, layers of InGaN 20 (and other ternary III-nitride semiconductormaterials) fabricated in accordance with embodiments of methods asdescribed herein, by formulating the precursor gas mixture such that aratio of a partial pressure of the nitrogen precursor to a partialpressure of the one or more Group III precursors within the chamber isat least about 5,600 (e.g., between about 5,600 and about 6,600), may beformed to have relatively smaller V-pits 30 therein relative topreviously known processes in which lower precursor ratios were employedduring fabrication of the layers of InGaN.

For example, semiconductor structures may be fabricated that comprise aternary III-nitride material, such as a layer of InGaN 20. The layer ofInGaN 20 may be fabricated by growing the layer of InGaN 20 on a layerof binary III-nitride material, such as a layer of GaN 16, using methodsas described hereinabove. The fully grown layer of InGaN 20 may have afinal average total thickness T (FIG. 4) greater than about one hundrednanometers (100 nm), greater than about one hundred and fifty nanometers(150 nm), or even greater than about two hundred nanometers (200 nm).The final average total thickness T may be less than a criticalthickness of the layer of InGaN 20. The layer of InGaN 20 may compriseat least five atomic percent (5 at %) indium, and may comprise betweenabout five atomic percent (5 at %) indium and about ten atomic percent(10 at %) indium. A relaxed lattice parameter mismatch between the fullygrown layer of InGaN 20 and the layer of GaN 16 may be at least about0.5% of the relaxed average lattice parameter of the layer of GaN 16,and may be between about 0.5% and about 1.0% of the relaxed averagelattice parameter of the layer of GaN 16. The fully grown layer of InGaN20 may comprise a plurality of V-pits 30 therein having an average pitwidth W (FIG. 5) of about two hundred nanometers (200 nm) or less, oreven about one hundred and fifty nanometers (150 nm) or less.

In the embodiments described above with reference to FIGS. 2 through 5,the semiconductor structure includes a single layer of InGaN 20 on asingle underlying layer of GaN 16. The methods described herein,however, also may be used to fabricate semiconductor structures thatinclude a plurality of layers of III-nitride material. For example, FIG.7 illustrates a semiconductor structure 100 that includes a substrate101 and a stack 102 comprising a plurality of layers of III-nitridematerial. The substrate 101 may comprise a substrate as previouslydescribed herein in relation to the substrate 10. The stack 102 maycomprise a plurality of layers of a binary III-nitride material, such aslayers of GaN 104, and a plurality of layers of a ternary III-nitridematerial, such as layers of InGaN 106. As shown in FIG. 7, the layers ofGaN 104 and the layers of InGaN 106 may be disposed in an alternatingfashion one over another, such that each layer of GaN 104 is separatedfrom other layers of GaN 104 by a layer of InGaN 106.

Each layer of GaN 104 may be substantially similar to, and may be formedin the same manner as, the previously described layer of GaN 16.Similarly, each layer of InGaN 106 may be substantially similar to, andmay be formed in the same manner as, the previously described layer ofInGaN 20. In the embodiment of FIG. 7, however, the layers of InGaN 106may be relatively thinner than the previously described layer of InGaN20. By way of example and not limitation, each of the layers of GaN 104and each of the layers of InGaN 106 may have a layer thickness ofbetween about two nanometers (2 nm) and about thirty nanometers (30 nm).The stack 102, however, may have a final average total thickness T likethat of the previously described layer of InGaN 20. For example, thestack 102 may have a final average total thickness T greater than aboutone hundred nanometers (100 nm), greater than about one hundred andfifty nanometers (150 nm), or even greater than about two hundrednanometers (200 nm).

As shown in FIG. 7, dislocations 110 may extend at least partiallythrough one or more of the layers of GaN 104 and the layers of InGaN106. These dislocations 110 may comprise dislocations as previouslydescribed in relation to the dislocations 18, 18′ of FIG. 4.Additionally, V-pits 112, like the previously described V-pits 30, maybe present within the stack 102. Each of the V-pits 112 may extend intothe stack 102 from an exposed major surface 103 thereof (the growthsurface), and may extend to an apex 108, which may originate at adislocation 110. As shown in FIG. 7, at least some of the V-pits 112 mayextend through a plurality of the alternating layers of GaN 104 andlayers of InGaN 106.

The layers of GaN 104 and the layers of InGaN 106 may be formed aspreviously described in relation to the layer of GaN 16 and the layer ofInGaN 20. In particular, each layer of InGaN 20 may be formed in areaction chamber using a precursor gas mixture that is formulated insuch a manner as to cause a ratio of a partial pressure of a nitrogenprecursor to a partial pressure of one or more Group III precursorswithin the chamber to be in a range extending from about 5,600 to about6,600, as previously described. As a result, the V-pits 112 may have arelatively smaller pit width W and/or pit depth D, as previouslydescribed with reference to FIG. 5.

Additional non-limiting embodiments of the disclosure are describedbelow.

Embodiment 1

A method of forming InGaN, comprising: providing a layer of GaN within achamber; epitaxially growing a layer of InGaN on a surface of the layerof GaN; and growing the layer of InGaN to an average final thicknessgreater than about one hundred nanometers (100 nm). Epitaxially growingthe layer of InGaN comprises: providing a precursor gas mixture withinthe chamber; selecting the precursor gas mixture to comprise one or moreGroup III precursors and a nitrogen precursor; formulating the precursorgas mixture to cause a ratio of a partial pressure of the nitrogenprecursor to a partial pressure of the one or more Group III precursorswithin the chamber to be at least about 5,600; and decomposing at leasta portion of the one or more Group III precursors and at least a portionof the nitrogen precursor proximate the surface of the layer of GaN.

Embodiment 2

The method of Embodiment 1, wherein formulating the precursor gasmixture to cause the ratio of the partial pressure of the nitrogenprecursor to the partial pressure of the one or more Group IIIprecursors within the chamber to be at least about 5,600 comprisesformulating the precursor gas mixture to cause the ratio to be in arange extending from 5,600 to 6,600.

Embodiment 3

The method of Embodiment 1, further comprising selecting the averagefinal thickness to be less than a critical thickness of the layer ofInGaN.

Embodiment 4

The method of any one of Embodiments 1 through 3, wherein epitaxiallygrowing the layer of InGaN on the surface of the layer of GaN comprisesdepositing the layer of InGaN on the surface of the layer of GaN using ahalide vapor phase epitaxy (HVPE) process or a metalorganic vapor phaseepitaxy (MOVPE) process.

Embodiment 5

The method of any one of Embodiments 1 through 4, wherein growing thelayer of InGaN to the average final thickness greater than about 100 nmcomprises growing the layer of InGaN to an average final thicknessgreater than about one hundred and fifty nanometers (150 nm).

Embodiment 6

The method of Embodiment 5, wherein growing the layer of InGaN to anaverage final thickness greater than about 150 nm comprises growing thelayer of InGaN to an average final thickness greater than about twohundred nanometers (200 nm).

Embodiment 7

The method of any one of Embodiments 1 through 6, wherein epitaxiallygrowing the layer of InGaN comprises formulating the layer of InGaN tohave a composition of In_(x)Ga_((1-x))N, wherein x is at least about0.05.

Embodiment 8

The method of Embodiment 7, wherein formulating the layer of InGaN tohave a composition of In_(x)Ga_((1-x))N, wherein x is at least about0.05 comprises formulating the layer of InGaN to have a composition ofIn_(x)Ga_((1-x))N, wherein x is between about 0.05 and about 0.10.

Embodiment 9

The method of any one of Embodiments 1 through 8, wherein epitaxiallygrowing the layer of InGaN on the surface of the layer of GaN furthercomprises formulating the layer of InGaN such that a relaxed latticeparameter mismatch between the layer of InGaN and the layer of GaN isbetween about 0.5% and about 1.0% of the relaxed average latticeparameter of the layer of GaN.

Embodiment 10

The method of any one of Embodiments 1 through 9, wherein growing thelayer of InGaN to an average final thickness further comprises forming aplurality of V-pits in the layer of InGaN having an average pit width ofabout two hundred nanometers (200 nm) or less.

Embodiment 11

The method of Embodiment 10, wherein forming the plurality of V-pitshaving an average pit width of about 200 nm or less comprises forming aplurality of V-pits having an average pit width of about one hundred andfifty nanometers (150 nm) or less.

Embodiment 12

The method of any one of Embodiments 1 through 11, further comprisingselecting the nitrogen precursor to comprise ammonia.

Embodiment 13

The method of any one of Embodiments 1 through 12, further comprisingselecting the one or more Group III precursors to comprisetrimethylindium and triethylgallium.

Embodiment 14

A method of forming a ternary III-nitride material comprising nitrogen,gallium, and at least one of indium and aluminum, comprising: providinga binary III-nitride material within a chamber; and epitaxially growinga layer of ternary III-nitride material on the binary III-nitridematerial. Epitaxial growth of the layer of ternary III-nitride materialincludes: providing a precursor gas mixture within the chamber, theprecursor gas mixture comprising a nitrogen precursor and two or moreGroup III precursors; formulating the precursor gas mixture such that aratio of a partial pressure of the nitrogen precursor to a partialpressure of the two or more Group III precursors within the chamber isat least about 5,600; and decomposing the nitrogen precursor and the twoor more Group III precursors in the chamber. The method further includesgrowing the layer of ternary III-nitride material to an average finalthickness greater than about one hundred nanometers (100 nm);formulating the layer of ternary III-nitride material such that arelaxed lattice parameter mismatch between the layer of ternaryIII-nitride material and the binary III-nitride material is at leastabout 0.5% of the relaxed average lattice parameter of the binaryIII-nitride material; and forming a plurality of V-pits in the layer ofternary III-nitride material, the plurality of V-pits having an averagepit width of about two hundred nanometers (200 nm) or less in the fullygrown layer of ternary III-nitride material.

Embodiment 15

The method of Embodiment 14, wherein formulating the precursor gasmixture such that the ratio of the partial pressure of the nitrogenprecursor to the partial pressure of the one or more Group IIIprecursors within the chamber is at least about 5,600 comprisesformulating the precursor gas mixture such that the ratio is in a rangeextending from 5,600 to 6,600.

Embodiment 16

The method of Embodiment 14, further comprising selecting the ternaryIII-nitride material to comprise indium gallium nitride.

Embodiment 17

The method of any one of Embodiments 14 through 16, further comprisingselecting the average final thickness to be less than a criticalthickness of the layer of ternary III-nitride material.

Embodiment 18

The method of any one of Embodiments 14 through 17, wherein growing thelayer of ternary III-nitride material to the average final thicknessgreater than about 100 nm comprises growing the layer of ternaryIII-nitride material to an average final thickness greater than aboutone hundred and fifty nanometers (150 nm).

Embodiment 19

The method of Embodiment 18, wherein growing the layer of ternaryIII-nitride material to an average final thickness greater than about150 nm comprises growing the layer of ternary III-nitride material to anaverage final thickness greater than about two hundred nanometers (200nm).

Embodiment 20

The method of any one of Embodiments 14 through 19, wherein formulatingthe layer of ternary III-nitride material such that a relaxed latticeparameter mismatch between the layer of ternary III-nitride material andthe binary III-nitride material is at least about 0.5% of the relaxedaverage lattice parameter of the binary III-nitride material comprisesformulating the layer of ternary III-nitride material such that arelaxed lattice parameter mismatch between the layer of ternaryIII-nitride material and the binary III-nitride material is at leastabout 5% of the relaxed average lattice parameter of the binaryIII-nitride material.

Embodiment 21

The method of any one of Embodiments 14 through 20, further comprisingselecting the nitrogen precursor to comprise ammonia.

Embodiment 22

The method of any one of Embodiments 14 through 21, further comprisingselecting the two or more Group III precursors to comprisetrimethylindium and triethylgallium.

Embodiment 23

A semiconductor structure comprising InGaN, the InGaN formed by a methodcomprising: providing a layer of GaN within a chamber; and epitaxiallygrowing a layer of InGaN on a surface of the layer of GaN. Epitaxialgrowth of the layer of InGaN comprises: providing a precursor gasmixture within the chamber; selecting the precursor gas mixture tocomprise one or more Group III precursors and a nitrogen precursor;formulating the precursor gas mixture to cause a ratio of a partialpressure of the nitrogen precursor to a partial pressure of the one ormore Group III precursors within the chamber to be at least about 5,600;and decomposing at least a portion of the one or more Group IIIprecursors and at least a portion of the nitrogen precursor proximatethe surface of the layer of GaN. In Embodiment 23, the fully grown layerof InGaN has an average final thickness greater than about one hundrednanometers (100 nm); a relaxed lattice parameter mismatch between thefully grown layer of InGaN and the layer of GaN is at least about 0.5%of the relaxed average lattice parameter of the layer of GaN; and thefully grown layer of InGaN comprises a plurality of V-pits thereinhaving an average pit width of about two hundred nanometers (200 nm) orless.

Embodiment 24

The semiconductor structure of Embodiment 23, wherein the layer of InGaNin formed in accordance with any one of Embodiments 1 through 13.

Embodiment 25

A semiconductor structure comprising a ternary III-nitride materialcomprising nitrogen, gallium, and at least one of indium and aluminum,the ternary III-nitride material foliated by a method comprising:providing a substrate comprising a binary III-nitride material within achamber; and epitaxially growing a layer of ternary III-nitride materialon the binary III-nitride material. Epitaxial growth of the layer ofternary III-nitride material includes: providing a precursor gas mixturewithin the chamber, the precursor gas mixture comprising a nitrogenprecursor and two or more Group III precursors; formulating theprecursor gas mixture such that a ratio of a partial pressure of thenitrogen precursor to a partial pressure of the two or more Group IIIprecursors within the chamber is at least about 5,600; and decomposingthe nitrogen precursor and the two or more Group III precursors in thechamber. In Embodiment 24, the fully grown layer of ternary III-nitridematerial has an average final thickness greater than about one hundrednanometers (100 nm); a relaxed lattice parameter mismatch between thefully grown layer of ternary III-nitride material and the binaryIII-nitride material is at least about 0.5% of the relaxed averagelattice parameter of the binary III-nitride material; and the fullygrown layer of ternary III-nitride material comprises a plurality ofV-pits therein having an average pit width of about two hundrednanometers (200 nm) or less.

Embodiment 26

The semiconductor structure of Embodiment 25, wherein the layer ofternary III-nitride material is formed in accordance with any one ofEmbodiments 14 through 22.

Embodiment 27

A method of forming a stack of layers of III-nitride material,comprising: providing a substrate within a chamber; epitaxially growingat least one layer of GaN and a plurality of layers of InGaN over thesubstrate within the chamber; and forming the stack of layers ofIII-nitride material to have a final average total thickness greaterthan about one hundred nanometers (100 nm), wherein epitaxial growth ofat least one layer of InGaN of the plurality of layers of InGaNcomprises: providing a precursor gas mixture within the chamber;selecting the precursor gas mixture to comprise one or more Group IIIprecursors and a nitrogen precursor; formulating the precursor gasmixture to cause a ratio of a partial pressure of the nitrogen precursorto a partial pressure of the one or more Group III precursors within thechamber to be at least about 5,600; and decomposing at least a portionof the one or more Group III precursors and at least a portion of thenitrogen precursor to form the at least one layer of InGaN.

The embodiments of the disclosure described above do not limit the scopeof the invention, since these embodiments are merely examples ofembodiments of the invention, which is defined by the scope of theappended claims and their legal equivalents. Any equivalent embodimentsare intended to be within the scope of this invention. Indeed, variousmodifications of the disclosure, in addition to those shown anddescribed herein, such as alternate useful combinations of the elementsdescribed, will become apparent to those skilled in the art from thedescription. Such modifications are also intended to fall within thescope of the appended claims.

What is claimed is:
 1. A semiconductor structure, comprising: a layer ofa first III-nitride material; and a layer of In_(x)Ga_((1-x))N, whereinx is at least about 0.05, on a surface of the layer of first III-nitridematerial, the layer of In_(x)Ga_((1-x))N having an average layerthickness of about one hundred nanometers (100 nm) or more, the layer ofIn_(x)Ga_((1-x))N comprising a plurality of V-pits therein having anaverage pit width of about two hundred nanometers (200 nm) or less. 2.The semiconductor structure of claim 1, wherein the plurality of V-pitshave an average pit width of about one hundred and fifty nanometers (150nm) or less.
 3. The semiconductor structure of claim 2, wherein x in thelayer of In_(x)Ga_((1-x))N is between about 0.05 and about 0.10.
 4. Thesemiconductor structure of claim 3, wherein the average layer thicknessof the layer of In_(x)Ga_((1-x))N is less than a critical thickness ofthe layer of In_(x)Ga_((1-x))N.
 5. The semiconductor structure of claim1, wherein the average layer thickness of the layer of In_(x)Ga_((1-x))Nis about one hundred and fifty nanometers (150 nm) or more.
 6. Thesemiconductor structure of claim 5, wherein the plurality of V-pits havean average pit width of about one hundred and fifty nanometers (150 nm)or less.
 7. The semiconductor structure of claim 6, wherein x in thelayer of In_(x)Ga_((1-x))N is between about 0.05 and about 0.10.
 8. Thesemiconductor structure of claim 7, wherein the average layer thicknessof the layer of In_(x)Ga_((1-x))N is less than a critical thickness ofthe layer of In_(x)Ga_((1-x))N.
 9. The semiconductor structure of claim1, wherein the average layer thickness of the layer of In_(x)Ga_((1-x))Nis about two hundred nanometers (200 nm) or more.
 10. The semiconductorstructure of claim 9, wherein the plurality of V-pits have an averagepit width of about one hundred and fifty nanometers (150 nm) or less.11. The semiconductor structure of claim 10, wherein x in the layer ofIn_(x)Ga_((1-x))N is between about 0.05 and about 0.10.
 12. Thesemiconductor structure of claim 11, wherein the average layer thicknessof the layer of In_(x)Ga_((1-x))N is less than a critical thickness ofthe layer of In_(x)Ga_((1-x))N.
 13. The semiconductor structure of claim1, wherein the layer of In_(x)Ga_((1-x))N comprises an epitaxial layerof In_(x)Ga_((1-x))N epitaxially grown on the layer of first III-nitridematerial.
 14. The semiconductor structure of claim 1, wherein a relaxedlattice parameter mismatch between the layer of InGaN and the layer offirst III-nitride material is at least about 0.5% of the relaxed averagelattice parameter of the layer of first III-nitride material.
 15. Thesemiconductor structure of claim 1, wherein the layer of firstIII-nitride material comprises a layer of GaN.
 16. A semiconductorstructure, comprising: a first III-nitride material; and epitaxialIn_(x)Ga_((1-x))N on the first III-nitride material, wherein x isbetween about 0.05 and about 0.10, the epitaxial In_(x)Ga_((1-x))Nhaving an average thickness over the first III-nitride material of abouttwo hundred nanometers (200 nm) or more, the epitaxial In_(x)Ga_((1-x))Ncomprising a plurality of V-pits therein having an average pit width ofabout one hundred and fifty nanometers (150 nm) or less.